Thermodynamics of TMU-TMU interaction in water, ethylene glycol and formamide – From pair solvophobic interaction to cluster formation

Abstract

This paper focuses on the interaction between tetramethylurea (TMU) molecules in liquid water, ethylene glycol (Eg) and formamide (FA) which form the H-bond network on a supramolecular level. The virial enthalpic, heat capacity, entropic and free energy parameters of solute–solute interaction have been extracted from the experimental thermodynamic data in a wide temperature range. The second virial coefficients of the TMU-TMU pair interaction and their temperature changes have been computed both in aqueous and non-aqueous systems. Our comparative analysis indicates that the strong solvophobic interaction between two TMU molecules does exist and increases with the temperature, the effect being much stronger pronounced in aqueous solutions. This strong attraction between methyl groups of TMU leads to formation of labile clusters containing both solute and solvent molecules.